Extreme pressure lubricants



Patented June 13, 1950 OFFICE EXTREME raassunu Luaarcms George M. McNnlty, Union, and Elmer B. Cypherl,

Cranford, N. J., alsignorl to Standard Oil Development Company, a corporation of Delaware No Drawing. Application January 22, 1947, Serial No. 723,054

4 Claims. (Cl- 252-463!) resultant injury to them. These conditions develop in various types of machinery, a common example being encountered in worm and hypoid gears which are used in automotive vehicles. In such cases it has been the practice in the past to include in lubricants chemicals which react with the metal parts themselves to form protective films on the metal surfaces. These films are of sub-microscopic thickness but have proved to be adequate to provide momentary surface protection until the lubricating film can be re-established.

Various compounds, usually including materials such as sulfur, chlorine, phosphorus and the like, have been included in extreme pressure lubricants and are usually compounded in such a way that they are relatively inactive at ordinary temperatures but become highly reactive with the metal parts being lubricated when the temperature is raised by high friction between the parts. When the oil film breaks under extremely high pressures the resultant high temperature causes an immediate chemical reaction to take place forming the protecting film of metal sulfide, chloride, phosphide, and the like.

The use of halogens and sulfur in oils and greases to impart extreme pressure characteristics thereto is well known in the prior art. It is known, furthermore, that inorganic sulfides and polysulfides may be reacted with halogenated hydrocarbons for like purposes. The use of certain organic sulfur containing compounds, in combination with halogenated hydrocarbons, is likewise known and the use of phosphorus sulfides has been suggested.

Although these compositions known to the prior art are relatively effective, they generally fall into two classes. One class, including the sulfur-chlorine products, generally carry high loads on the SAE extreme pressure testing machine, and are quite satisfactory for the lubrication of passenger cars and light trucks, but carry relatively low loads on the Timken machine and are relatively ineirective in heavy truck operations under low speed and high torque conditions. The other class, including sulfur-phosphorus products, generally carry high loads on the Timken machine, and are satisfactory for heavy truck duty, but are relatively ineffective on the SAE machine and in high speed passenger car operations.

One object of our invention is to combine chemical ingredients in a novel manner to provide lubricants having good load-carrying properties on both the Timken and the SAE machines for use in so-called universal gear lubricants suitable for both passenger car and heavy duty truck operations. Such a lubricant would have a distinct advantage over conventional gear lubricants because only one product would have to be carried in stock where both types of operations are encountered. This would eliminate failures caused by the use of the wrong type of lubricant, and is especially important in military operations where problems of supply are often acute.

A further object of our invention is to provide lubricants havin superior load-carrying characteristics while at the same time being relatively non-corrosive toward the metals they encounter.

By our invention the alkali salt of an organic thiophosphoric acid is reacted at ordinary temperatures or at temperatures from 20 C. to C. with a halogenated hydrocarbon such as chlorinated kerosene or chlorinated paraflin wax or both with or without the addition of an alkali hydrosuliide or polysulflde. A condensation takes place with elimination of alkali metal halide, thus removing one chlorine or other halogen atom from the halogenated paraffin wax or kerosene. The chlorine content of the latter, however, is substantial, e. g. from about 20 to at least 34%. as indicated in examples cited hereinafter, so the residual halogen content is substantial.

The organic thiophosphoric acids, namely alkyl and/or aryl thiophosphoric acids, are conveniently prepared by reaction of alcohols with sulfides of phosphorus, such as P285. In practicing our invention alcohols of 1 to 12 carbon atoms are most advantageously employed, and preferably those having 1 to 6 carbon atoms, such as methyl, ethyl, isopropyl, hexyl, etc. In practicing our invention it is also possible to employ as reactants aryl thiophosphoric acids, prepared by the treatment of phenols or alkylated phenols with sulfides of phosphorus, but the alkyl' thiophosphoric acids are preferred.

The reaction products of such materials yield additives which have unusually eifective extreme pressure properties and thus are effective to reduce the wear on mechanical elements such as hypoid gears, worm gears and the like.

To illustrate the materials used, the following examples are given:

Example 1.540 grams of 91% isopropyl alcohol, 60 grams of di-isopropyl dithlophosphoric acid, and 44 grams of a 25% aqueous solution of sodium hydroxide were stirred and refluxed in aglass flask. (The di-isopropyl dithiophosphoric acid was prepared by reaction of isopropyl alcohol and phosphorus pentasulilde.) After cooling, 320 grams of chlorinated kerosene containd phates wherein a chloralhl compound, i. e. a chlorinated hydrocarbon of the type representative of kerosene or paraifln wax is added to provide a considerable quantity of active chlorine for extreme pressure use.

The following table indicates comparative results which were obtained by tests on the Tlmken lubricant testing machine and the SAE extreme pressure testing machine, comparing the untreated oil, the same oil containing each of two standard extreme pressure agents. and the same lubricant with the reaction products described above added in the same proportions. The results of the tests were as follows:

Timken and SAE machine tests Timken Machine e... Lubricant c fi gg Bear width Unit Load, 3 g Lew-Arm in 04th In. Lbs/Sq. In.

Untreated lubrica nil 1. 65 7, 860 m Lubricating oil 731 1 1095 or standard high-speed type E. P.

additive 8 2. 62 3, m 325 Lubricating oil with 10% of standard high-torque type E. P.

ddi i i is; 23g Lubricatin oil with 107 of Example 1 a t ve Luhrimtin: oil with 107?, of Example 2 additive 61 1. 9s ,soo m ing 40% chlorine and 216 grams of a chlorinated paraflln wax containing 34% chlorine were added. The mixture was stirred and refluxed for two hours. The aqueous layer was then separated and discarded and the remainder of the reaction product was vacuum stripped to remove alcohol and water. Thereafter, the product was filtered, and was found to contain 0.99% phosphorus, 2.20% sulfur, and 33.74% chlorine.

The foregoing reactions were carried out at a convenient refluxing temperature for isopropyl alcohol, preferably just above the boiling point of the alcohol solution which is about 185 F. Isopropyl alcohol per se boils at about 180 F. under normal pressures.

Example -2.1080 grams of 91% lsopropyl alcohol, 120 grams of di-isopropyl thiophosphoric acid, 88 grams of aqueous sodium hydroxide solution, and 1080 grams of chlorinated paraffin wax containing approximately 20% chlorine were reacted and treated as in Example 1. Analysis showed that this product contained 0.44% phosphorus, 0.88% sulfur, and 20.92%

chlorine.

The products described above were combined in the proportions of 10% with 90% of a standard base lubricating oil consisting of 35% Mid- Continent steam cylinder oil, 64.5% of an SAE 20 solvent extracted Mid-Continent oil and 0.5% of a standard pour point depressant, commonly used in such lubricants. The proportions of mineral oil and additive may be varied considerably, but in general they will lie between 80% and 99% oil and 20% to 1% extreme pressure additive.

The compositions described above in Examples 1 and 2 have the general formula mo s-a.

where R1 is an alkyl radical having 1 to 12 carbon atoms, R: is chlorinated kerosene or chlorinated paraflln wax. The materials may be described broadly as chloralkyl substituted phos- The. high-speed type extreme pressure additive listed in the second line of the preceding table has been found to be satisfactory for passenger car lubrication, where conditions of high speed and low torque normally prevail. It has failed, however, under conditions of high torque and low speed as exemplified by heavy truck service, and particularly in the U. 8. Army Ordnance Department's AXE-1570 high torque test. It also carries a very low load on the Timken machine, which appears to correlate with the AXS-1570 test.

The high-torque type extreme pressure additive, listed as the third item of the table, carries a high load on the Timken machine and has passed the AXS-1570 test, but is considered of doubtful value for passenger car lubrication because of the relatively low load carried on the SAE machine.

The superiority of the additives of the present invention is readily apparent, as shown by the high load-carrying properties of Examples 1 and 2 on both the Timken and the SAE'machines, making it possible to prepare a single lubricant suitable for lubricating all types of automotive equipment. A simple mixture of both types of the standard additives is not satisfactory for either type of operation. The reaction products prepared in Examples 1 and 2 provide very satisfactory extreme pressure additives for lubricating oils and greases which have superior loadcarrying properties and are substantially free of corrosive properties. It may be preferred, however, in some cases, to use a corrosion inhibitor in small quantities in addition to the extreme pressure additive.

It will be understood that various types of lubricants may be treated with these extreme pressure additives and that they may be combined with either mineral or fatty oils or mixtures thereof in any suitable proportions. Preferably, the reaction products will be added in quantities of from 2.0% to 15%, although as indicated above these limits may be exceeded in some cases. In mam; cases, the extreme pressure additive material will be prepared in concentrated form so that it may be added in any desired quantities to lubricating oils and greases to impart desired loadcarrying properties thereto. although the preparation of a finished lubricant by direct reaction in the presence 01' mineral oil is also contemplated.

It will, of course, be understood that various other additives such as pour point depressants, corrosion inhibitors, detergents and the like may be added to the oil or grease which forms the base of the lubricant in various proportions as required for the particular surface and operating conditions intended. We are aware of the tact that various reaction products containing both sulfur and halogen have been used in the past for extreme pressure properties and that extreme pressure agents produced by the reaction of alkali metal alkyl mercaptides with halogenated hydrocarbons have been known. The particular reaction products described above. however. are

novel and highly effective for the purposes described.

We claim:

1. An extreme pressure additive for lubricant compositions consisting essentially of the condensation product, at a temperature within the range of 20 to 150 C., of approximately 1 part by weight of a chlorinated hydrocarbon, selected from the class which consists oi chlorinated kerosene and chlorinated wax, and about 9 parts by weight of a dialkyl dlthiophosphoric acid alkali salt having 1 to 6 carbon atoms in each of the alkyl groups, said product having a chlorine con tent of between about 20 and 34% by weight.

2. An additive according to claim 1 in which each of the alkyl groups is an isopropyl group.

3. An extreme pressure lubricant composition consisting essentially of mineral base lubricating oil containing from 1 to 20% by weight of the condensation product, at a temperature within the range of 20 to 150 C., of approximately 1 part by weight of a chlorinated hydrocarbon, se-

lected from the class which consists of chlorinated kerosene and chlorinated wax, and about 9 parts by weight of a dialkyl dithiophosphoric acid alkali salt having 1 to 6 carbon atoms in each of the alkyl groups, said product having a chlorine content of between about 20 and 34% by weight.

4. A composition according to claim 3 wherein each 01' the alkyl groups in said condensation product is an isopropyl group.

GEORGE M. MoNULTY.

ELNHEIR B. CYPHERS.

REFERENCES. CITED The. following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 2,063,629 Salzberg et al Dec. 8, 1936 2,167,867 Benning Aug. 1, 1939 2,242,260 Prutton May 20, 1941 2,266,514 Romieux et a1 Dec. 16, 1941 r 2,307,183 Zimmer et al Jan. 5, 1943 2,358,305 Cook et al Sept. 19, 1944 

1. AN EXTREME PRESSURE ADDITIVE FOR LUBRICANT COMPOSITIONS CONSISTING ESSENTIALLY OF THE CONDENSATION PRODUCT, AT A TEMPERATURE WITHIN THE RANGE OF 20* TO 150*C., OF APPROXIMATELY 1 PART BY WEIGHT OF A CHLORINATED HYDROCARBON, SELECTED FROM THE CLASS WHICH CONSISTS OF CHLORINATED KEROSENE AND CHLORINATED WAX, AND ABOUT 9 PARTS BY WEIGHT OF A DIALKYL DITHIOPHOSPHORIC ACID ALKALI SALT HAVING 1 TO 6 CARBON ATOMS IN EACH OF THE ALLKYL GROUPS, SAID PRODUCT HAVING A CHLORINE CONTENT OF BETWEEN ABOUT 20 AND 34% BY WEIGHT. 